QwtLegend items disappear when checked off

[steve123]

I've got a plot with a legend that initially appears ok. However, when I click on an item in the legend to deselect it (uncheck it?) it is not only unchecked, but it disappears from the legend entirely. Furthermore, I never get a signal when an item on the legend is clicked.

Here is part of my code (I have left out quite a bit of code from this class):
In the constructor of my class, plot_ is a QwtPlot*:

QwtLegend * legend = new QwtLegend();
    legend->setItemMode(QwtLegend::CheckableItem);
    legend->setWhatsThis("Click on an item to show/hide the plot");
    plot_->insertLegend(legend, QwtPlot::RightLegend);
    connect(plot_, SIGNAL(legendChecked(QwtPlotItem *, bool)),this,
        SLOT(showCurve(QwtPlotItem *, bool)));

QwtLegend * legend = new QwtLegend();
    legend->setItemMode(QwtLegend::CheckableItem);
    legend->setWhatsThis("Click on an item to show/hide the plot");
    plot_->insertLegend(legend, QwtPlot::RightLegend);
    connect(plot_, SIGNAL(legendChecked(QwtPlotItem *, bool)),this,
        SLOT(showCurve(QwtPlotItem *, bool)));

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Later on, when I add a new curve (newSpec is a QwtPlotSpectrogram* ):

newSpec->setItemAttribute(QwtPlotItem::Legend, true); // add to the clickable legend
        newSpec->updateLegend(plot_->legend());

newSpec->setItemAttribute(QwtPlotItem::Legend, true); // add to the clickable legend
        newSpec->updateLegend(plot_->legend());

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I assume the two problems (signal not set up correctly, items disappearing) are related but I can't figure out why or how to solve it. Thank you very much!

Edit: forgot to mention, if this helps, the itemCount() of the legend does change (decreases by 1) when one of the legend items disappears.

[Uwe]

Check the cpuplot example,

Uwe

[steve123]

Hi Uwe,

Thanks for your quick reply. It turns out I should not have been using attach() but rather setVisible, as your example does. Thanks!